This application is based on Japanese Patent Application No.Hei 11-179916 filed on Jun. 25, 1999 and No.Hei 11-337645 filed on November 29, the contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to a rotary electric machine and a method for making the same, and particularly to a rotary electric machine for an AC generator driven by an engine mounted on a vehicle, such as a passenger car, truck or vessel.
2. Description of Related Art
WO98/54823 discloses a stator for a vehicle AC generator having a stator winding which is assembled by connecting opposite ends of a plurality of conductor segments. These conductor segments are inserted into slots which are axially extended along the stator core. At the coil ends of the stator, the segments form a regularly inclined pattern on each layer so that a collision of the segments at the coil ends is avoided. Such a stator is designed for increasing the output power based on reducing heat loss in the stator winding and improving the slot-space factor (the ratio of the conductors to the cross-sectional area of the slot).
On the other hand, in a conventional rotary electric machine, such as disclosed in WO98/54823, several factors, such as the number of turn of the winding, the inside diameter D of the stator core and the axial length L of the stator core, are defined based on the required performances, such as an output voltage and a starting speed.
However, vehicles are produced in several different varieties, such that engine capacity and an assumed electric load are variable. Accordingly, the AC generators for vehicles are designed for several different specifications in accordance with these varieties. Therefore, manufacturers are required to produce each different stator in accordance with these variables, and to produce corresponding adaptive rotors and frames. It is further required to design the adaptive manufacturing machines and the specifications on the basis of the required performance.
The present invention addresses these drawbacks by providing an improved stator arrangement.
It is therefore an object of this invention to provide a rotary electric machine which has a reduced number of stator windings and method for making the same.
It is a further object of this invention to provide a rotary electric machine which accommodates the electric conductors only in a part of the slots and method for making the same.
It is another object of this invention to provide a rotary electric machine which accommodates the electric conductors in the slot less than the electric conductors primarily permissible to disposed in a slot.
It is a still further object of this invention to improve a cooling efficiency of the stator.
It is a yet further object of this invention to provide a rotary electric machine adaptable to a plurality of required performances and method for making the same.
It is still another object of this invention to provide a rotary electric machine adaptable to a plurality of required performances and to change these required performances in the future and to provide a method for making the same.
According to a first aspect of the present invention, a stator has at least one unused slot and a slot having an unused layer. The present invention provides a stator winding having a reduced number of turns or a reduced cross-sectional area. For instance, it is possible to provide two or more output types of the AC generators using common stators.
The unused slot and the unused layer may provide the cooling medium passages to improve a cooling efficiency of the stator. On the other hand, the unused slot and the unused layer may be plugged in order to provide highly rigidity.
The stator winding is preferably forms of a plurality of U-shaped conductor segments. This configuration provides an advantageous manufacturing process.
According to an another aspect of the present invention, a stator core is provided having a plurality of base slots and a plurality of reserve slots. Additionally, the base slots define base teeth between adjacent two of them. Each of the base teeth has a circumferential width. The width is still enough to form the reserve slot andareserve teeth, even if the base tooth includes one or more reserve slots which is same as the base slot. The reserve teeth are located on both sides of the reserve slots. In this configuration, it is possible to increase the variety of outputs by changing the manufacturing equipment only a little. The reserve slots include both actually formed slots and imaginary slots.
According to an another aspect of the present invention, the stator has a first slot in which the stator winding is accommodated and a second slot in which the stator winding is not accommodated. The present invention provides a stator winding having a reduced number of turns or a reduced cross-sectional area. For instance, it is possible to provide two or more output types of the AC generators using common stators.
According to another object of the present invention, a method for manufacturing the AC generator for vehicle includes a step for positioning the stator winding with a plurality of used slots to reserve a plurality of empty slots as the reserve slots.
Other features and advantages of the present invention will be appreciated, as well as methods of operation and the function of the related parts, from a study of the following detailed description, the appended claims, and the drawings, all of which form a part of this application.